Use of High-Power Diode Laser Arrays for Pre- and Post-Weld Heating during Friction Stir Welding of Steels

Abstract

In this research a high-power diode laser array was used to preheat HY-80 steel to determine the efficacy of using a diode laser array for preheating prior to friction stir welding in order to reduce frictional forces thereby reducing tool wear and increasing welding speeds. Using instrumented plates the temperature profile using diode heating alone was determined in order to validate theoretical models. A high-power diode laser is proposed as a more cost effective and efficient means of preheating compared to other hybrid friction stir welding techniques. Parameters of the diode array were easily controllable and resulted in a preheated area that very closely matches the typical stir zone observed in friction stir welds. A proposed diode laser assisted friction stir welding system is presented, and it is hypothesized that the addition of diode laser preheating will improve tool life and/or increase welding speeds on steels.

Analysis of High-Power Diode Laser Heating Effects on HY-80 Steel for Laser Assisted Friction Stir Welding Applications

“…Several plates of HY-80 were laser heated in accordance to the procedure discussed in related research [17]. The HPDL used was a 5 kW Northrup Grumman diode array that emits partially-coherent light at a wavelength of 795 nm.…”

“…Figure 1 shows a series of experimental runs to measure of beam profile and establish the operating conditions of the HPDL array [17]. speed and 100 millimeters per minute (MMPM) for traverse or scan speed [25].…”

“…Many of the original hybrid FSW techniques used traditional fusion welding heat input mechanisms, but more recently laser-based hybrid FSW concepts have been proposed that offer simple, effective, and controllable means of preheating [14] [15] [16] [17]. Frictional forces are directly related to the downward force of the tool as well as the shear force once the tool is rotating [3] [18] [19].…”

“…The advantages and potential applica-tions of HPDL systems are discussed in detail in reviews by Li [20], Chen [21], and Bachmann [22]. Additionally, HPDLs can have adjustable wavelengths allowing for increased absorption and efficiency further adding to their flexibility [17]. Assisting FSW with the use of HPDL systems was initially proposed as Diode Laser Assisted Friction Stir Welding (DLAFSW), where the flexibility of HPDL systems was a key consideration for controlling preheating and post FSW cooling on hardenable steels [17].…”

“…Additionally, HPDLs can have adjustable wavelengths allowing for increased absorption and efficiency further adding to their flexibility [17]. Assisting FSW with the use of HPDL systems was initially proposed as Diode Laser Assisted Friction Stir Welding (DLAFSW), where the flexibility of HPDL systems was a key consideration for controlling preheating and post FSW cooling on hardenable steels [17]. This research aims to add to that proposal by characterizing the microstructural changes due to laser heating with HPDLs alone.…”